Push switches are known as button switches used in, for example, portable and on-board audio devices and digital camera VTRs and mobile communication devices such as cellular phones.
FIG. 15 is a sectional view illustrating a push switch 100 described in Patent Literature 1.
The push switch 100 includes a substrate 101, a movable member 102, a first pressing member 103, a second pressing member 104, a housing 105, a first fixed contact point 106, and second fixed contact points 107.
The substrate 101 includes a recess formed in its surface, the first fixed contact point 106 is disposed at the center of the recess, and the second fixed contact points 107 are disposed around the recess. The movable member 102 is a dome-shaped flexible conductive member, and is disposed so that its end parts are in contact with the second fixed contact points 107. The first pressing member 103 is a resin sheet member forming two connected disks having different diameters. The second pressing member 104 is a hemispherical member made of a synthetic resin. The bottom surface of the second pressing member 104 is bonded to the lower surface of the first pressing member 103, and the top of the spherical surface of the second pressing member 104 is in contact with the top of the movable member 102. The housing 105 is bonded to the upper part of the substrate 101 to form, together with the recess in the substrate 101, a space for accommodating the movable member 102, the lower part of the first pressing member 103, and the second pressing member 104.
When the upper surface of the first pressing member 103 is pressed, the curve of the movable member 102 is inverted so that the central portion, including the top, of the movable member 102 comes into contact with the first fixed contact point 106. When the top of the movable member 102 comes into contact with the first fixed contact point 106, the first fixed contact point 106 and the second fixed contact points 107 establish conduction between them via the movable member 102.
When the upper surface of the first pressing member 103 is pressed, the movable member 102 functions as a spring which generates a spring load acting opposite to a force that presses the upper surface of the first pressing member 103. Upon pressing of the upper surface of the first pressing member 103, the spring load of the movable member 102 that acts opposite to the pressing direction produces a sense of click.
Patent Literature 2 discloses a thin switch capable of ensuring a sufficient stroke length in switch operation and improving a feeling upon switch operation. The thin switch described in Patent Literature 2 includes a surface sheet, a dome sheet, a movable contact point, a fixed contact point, a spacer, and an elastic member. The dome sheet includes a dome portion bulging in a dome shape. The movable contact point is disposed on the lower surface of the dome portion. The fixed contact point is opposed to the movable contact point. The spacer opposes the lower surface of the surface sheet to the upper surface of the dome portion. The elastic member is interposed between the lower surface of the surface sheet 2 and the upper surface of the dome portion, and elastically deforms earlier than the dome portion for a pressing load received by the upper surface of the surface sheet.